结直肠癌是常见的恶性肿瘤，极易复发转移。黏蛋白型O-聚糖是肠道上皮细胞黏液层的主要成分，在结直肠癌的发病过程中常表达异常，但具体机制不明。本项目在前期工作基础上，（1）利用黏蛋白型O-聚糖缺陷的小鼠和细胞株（LS174T），以O-型糖基化反应为视角探索肿瘤的发生发展、转移及相关分子机制；（2）检测黏蛋白型O-聚糖在人结直肠癌原发灶和转移灶的异常表达及与临床转归的关系；（3）采用流式细胞分选和激光捕获显微切割（LCM）技术分离O-聚糖异常表达的人结直肠癌细胞，然后采用外显子捕捉测序、定量PCR和MassARRAY甲基化检测等技术探索O-聚糖异常表达的分子机制。我们还拟采用表达谱分析技术检测与O-聚糖异常表达相关的差异基因及分子事件，以阐明黏蛋白型O-聚糖生物学作用的分子机制及调控环节。本项目首次在糖生物学水平上探索结直肠癌发生及转移的机理，对于肿瘤早期诊断、病程监测、预后评估均有重要意义。

Colorectal cancer is a leading cause of cancer-related death around the world but there are no reliable treatments available. It is very hard to completely cure colorectal cancer especially for metastatic cancers. O-linked oligosaccharides (O-glycans) are the primary components of the intestinal mucus layer that overlies the gastrointestinal epithelium. Notably, altered intestinal O-glycan expression are seen in over 80% of colorectal cancers, however, whether or not this abnormal O-glycan expression contributes to the etiology of colorectal cancer is unknown. Our previous studies have created mice lacking intestinal O-glycans and we found that O-glycan-/- mice develop spontaneous colorectal adenocarcinoma. In this study, we intend to investigate the role of mucin-type O-glycans in the development and metastasis of colorectal cancer in O-glycan-/- mice. In the meanwhile, we aim to examine if mucin-type O-glycan-mediated O-glycosylation plays a contributory role in cancer cell apoptosis, proliferation, invasion by culturing LS174T cells harboring aberrant O-glycans. We also investigate the frequency of abnormal O-glycosylation in human primary and metastatic colorectal cancer, as well as the relationship between abnormal O-glycosylation and the clinical features. Once we get some significant results, we will specifically isolate Tn antigen positive tumor cells (which is a specific marker for abnormal mucin-type O-glycans) through laser capture microdissection (LCM) and FACS, respectively. Then, we are going to use exome capture sequencing, qRT-PCR, and analysis of the promoter methylation by MassARRAY to explore the underlying mechanisms related to abnormal expression of mucin-type O-glycans in these collected human tumor cells. Finally, we will use gene expression microarray to analyze the expression of the relevant genes and signaling pathways related to abnormal O-glycosylation. Our study will disclose some novel mechanisms regarding the role of O-glycosylation in the development and metastasis of colorectal cancer and provide some clues for their early diagnosis and targeted therapies in clinical settings.